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(11) | EP 0 644 339 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Anti-cross thread fastener with cleaning tip |
| (57) A threaded fastener (10) has an eccentric tip (16) with a smooth portion (26), a
threaded portion (28) and a cleaning recess (30) formed into the threaded portion
(28) of the tip (16). The recess (30) nd tip (16) are formed in the heading operation
prior to rolling the threads onto the shank (14) which provides better thread quality. |
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] The present invention relates to threaded fasteners and, more particularly, to anti-cross thread screws or fasteners with cleaning points.
[0002] When a screw or bolt is screwed into a threaded nut or port, where the port is subjected to foreign materials such as dust, dirt, weld splatter, paint or the like, the foreign material is carried into the mating area between the external and internal threads as the screw or fastener is threaded into the port. If foreign material is carried into the threads, galling and/or seizing usually results during assembly. This galling and seizing of the bolts causes substantial down time during an assembly operation, since the seize fastener must be removed, the hole cleaned out and a replacement fastener installed.
[0003] A common problem exists in the fastener field with cross threading. Cross threading generally occurs when the threaded fastener is received into a threaded nut or hole wherein the threads are in misalignment. Typical misalignments are axial and angular misalignments. In an axial misalignment, the axis of the shank of the screw is parallel with, but not colinear with, the axis of the receiving nut or hole. In an angular misalignment, the axis of the shank of the bolt is at an angle with respect to the axis of the nut or threaded hole. These misalignments cause the fasteners to be cross threaded and generally lead to seizing of the fasteners. The seizing causes a detrimental effect to both the bolt and nut, generally ruining one, the other or both, and causing little or no clamp load in the joint.
[0004] U.S. Patent Number 4,952,110 illustrates an anti-cross threading screw. This fastener satisfactorily provides for anti-cross threading, but fails to provide a cleaning function. The present invention is an improvement over this patent. Accordingly, U.S. Patent No. 4,952,110, the specification and drawings, is expressly herein incorporated by reference.
[0005] A traditional method of forming recesses or flutes onto a bolt is during the thread rolling operation. It requires a notch to be cut into the thread die, a fluter insert is positioned into the notch and as the part goes through the thread die, when it hits the fluter insert, it takes the form of the flute. A disadvantage in this type of method is that when the bolt goes through the thread die and hits the flute, it has a turbulent effect and the bolt wants to slip. A so-called drunken, thread or a poor quality thread can result from this condition.
[0006] The method of the present invention provides forming the recess during the heading operation while forming the tip. By forming the recess or flute during the heading operation while forming the tip, when the part is placed into the thread die, there is no turbulence while the threads are applied on the bolt, thus forming good quality threads without the use of fluter inserts.
[0007] From the following detailed description of the present invention taken in conjunction with the accompanying drawings and claims, other objects and advantages of the present invention will become apparent to those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 6 is a vertical cross section view of Figure 1 taken through the plane designated by the line 6-6 thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] Turning to the figures, particularly Figure 1, a threaded fastener bolt is illustrated and designated with the reference numeral 10. The threaded bolt 10 includes a head 12, a shank 14 projecting from the head 12, and a tip 16 at the end of the shank 14 opposing the head 12. Also, a washer 18 may be positioned adjacent the head 12.
[0017] The head 12 may be adapted to be engaged by a tool for applying rotational torque. The head may be slotted to receive a flat or Phillips head screw driver, or may be formed as shown with a hex head to provide flat areas for receiving a wrench or a variety of other drive configurations.
[0018] The shank 14 includes a threaded peripheral surface 20 and predetermined major and minor thread diameters. The peripheral surface 20 is continuous about the shank 14 having an arc circle of 360°. Generally, the shank 14 has a substantially circular cross section and a longitudinal axis 22.
[0019] The tip 16 projects from the shank 14 and defines an axis 24 which is eccentric and generally parallel with the axis 22 of the shank. The tip 16 includes a non-threaded, relatively smooth portion 26 and a partially threaded portion 28 with a recess 30 in the partially threaded portion 28. The partially threaded portion 28 has a peripheral surface, which is on an arc substantially coincident and continuous with the peripheral arc of the shank surface 20. The portion 28 is continuous with and on a longitudinal line 32 when viewed in side elevation, as shown in Figure 2. Generally, the portion 28 has zero to one or more partial threads opposing the smooth portion 26 and substantially aligned on a longitudinal line 34, which defines an edge of the major thread diameters when viewed in a side elevation, as shown in Figure 2.
[0020] The recess or flute 30 extends from the end of the tip along the partially threaded portion 28 into at least one of the full threads on the shank. The recess or flute 30 has an overall rectangular shape or it may be elliptical, and when viewed in plan, as in Figure 5, is positioned 180° with respect to the center of the smooth portion 26. The recess 30 has a uniform depth and follows along both the tip and shank portion. The recess has a thickness which is about 10% to 33% of the diameter of the shank 14.
[0021] The tip smooth portion 26 has an arcuate peripheral surface 40. The edge 41 of surface 40 defines a curve with respect to the longitudinal axes having an arcuate slope of a predetermined radius 42 when viewed in a side or top elevation as seen in Figures 2 and 4. The slope of the edge 41 is concave with respect to the line 44. The radius 42 is at a ratio with respect to the major thread diameter at from about 4.5:1 to about 0.5:1 and more preferably from about 2.1 to about 1.2:1. The ends 45 and 46 of the surface 40 continuously blend into the threaded portion of the shank. The tip 16, in cross section, has a non-circular cross section, as seen in Figure 6. The section 26 covers approximately from about 40% to about 80%, preferably from about 50% to 70% of the periphery of the tip 16.
[0022] Turning to Figures 7 and 8, dies are illustrated for manufacturing the fastener tip as described above. First, a blank 50 is provided of a desired diameter. The blank is forced into dies, only the die 52 is shown, to form an unthreaded fastener having a head, desired shank diameter as well as the tip 16. Also, simultaneously with forming the above described fastener, the recess 30 is formed in the blank 50. As can be seen from the die 52, the member 58 extends a uniform distance into the die aperture opposing the arcuate portion, which forms smooth surface 26. Thus, the member forms a uniform depth in the recess tip and shank. Also, as can be seen in Figure 8, the member 58 has an overall rectangular shape to form the rectangular recess.
[0023] After the tip and recess is formed in the shank and tip, the threads are rolled onto the shank. The threads are rolled underneath the portion of the tip as described. After rolling the threads, if desired, a coating, lubricant or the like may be added to the threads. After the process, a bolt is formed like that illustrated above.
[0024] The present bolt provides a recess to accumulate foreign material that would be otherwise carried into the mating area between the external and internal threads. Thus, the present invention eliminates the possibility of galling and seizing, which happen when foreign material is carried into the threads during assembly. Further, the invention provides an anti-cross thread screw with a cleaning recess.
1. A fastener comprising a head and a threaded shank projecting from said head, said
shank having a desired radius, an arcuate peripheral surface, a substantially circular
axial cross section and a tip at its axial end opposite said head, said tip comprised
of a first portion having a surface with one or more partial threads, and a second
portion having a smooth peripheral surface with its edge defining a curve with respect
to the longitudinal axis, said first portion and second portion being continuous with
one another and said tip including an axis being offset with respect to said shank
axis, and a recess formed on said threaded first portion of said tip said recess for
receiving foreign material.
2. A fastener comprising a head and a threaded shank projecting from said head, said
shank having a desired radius, an arcuate peripheral surface, a substantially circular
axial cross section and a tip at its axial end opposite said head, said tip comprised
of a first portion having a surface with zero or one or more partial threads, the
periphery of the one or more partial threads is on an arc substantially coincident
and continuous with the peripheral arcuate surface of full threads on said shank such
that a radius of said arc is substantially the same as said shank radius, and a second
portion having a smooth peripheral surface with its edge defining a curve with respect
to the longitudinal axis, said first portion and second portion being continuous with
one another having a non-circular axial cross section and said tip including an axis
begin offset with respect to said shank axis, and a recess formed on said threaded
first portion of said tip said recess for receiving foreign material.
3. The fastener according to claim 1 or 2, wherein said recess is at the end of said
tip and extends through at least the first full thread on said shank.
4. The fastener according to claim 1, 2 or 3, wherein said recess is positioned 180°
from the center of the smooth portion of the tip.
5. The fastener according to any one of the claims 1-4, wherein said recess has a width
proportional to said shank diameter, preferably about 10% to 33% of the shank diameter.
6. The fastener according to any one of the preceding claims, wherein said recess has
an overall rectangular or elliptical shape.
7. A method of manufacturing a fastener comprising forming a blank having a head and
an unthreaded shank, forming said blank into a header die means, forming a tip having
a smooth peripheral surface with its edge defining a curve with respect to a longitudinal
axis and a recess in said tip opposing said smooth peripheral surface, forming threads
on said shank and on said tip opposite said smooth peripheral surface such that said
recess extends from said tip through at least a first full thread.
8. The method according to claim 7, further comprising forming said recess to have an
overall rectangular or elliptical shape.
9. The method according to claim 7 or 8, further forming said recess in said shank and
tip with a unifom depth.
10. The method according to claim 7, 8 or 9, wherein said recess width has a size equal
to about 10% or 33% of the diameter of said shank.